Lathe cross slide issues

I'm hoping to get some advice on my problem with my cross slide. When facing I hnoticed its not cutting flat but a slight convex or cone. I've dismantled the carriage inspected and cleaned. I did the same with the cross slide. Only thing I noticed was the gib had a slight bow maybe .002. I deburred all the edges,cleaned,oiled and reassembled everything.
I placed a .0005 indicator in the 3 jaw ran the carriage up and when running the cross slide through its travel the dial doesn't move til about two thirds of the travel then consistently moves about .003 total through the last third of its travel. I had the same reading prior to disassembly that's what prompted the investigation.
I'm guessing that the dovetails will need to get scraped perpendicular to the carriage,then the cross slide to the dovetails? And where I could bring to have this done. I think it would be to much for me without the proper knowledge and tooling. Any input would be much appreciated.

Sounds like the dovetail way is bowed - worn at the ends from dirt ingress. I have been scraping the exact same fault out of a cross slide today. I was surprised at how pronounced the wear was.

What kind of lathe?

The machine is made so the cross slide cuts the part that way. Usually about .0004" /12". So when you set the shaft on flat surface it doesn't turn over. Then as the bed wears front left inside way it gets worse. Gibs always are bowed or bent because they wear on one side. Like grinding one side of metal it warps up. Rich

I am curious about what you would find with an indicator in the chuck, measuring off a ruler held in the toolpost or secured to the compound. The test would be to run the carriage up to the chuck as you normally would, clamp it for facing, then use the indicator to measure the position of the ruler in the front and the back, and look at the difference. After recording this difference, run the carriage further in towards the chuck, back it out to about the same position it was before and clamp it in place. Repeat the measurements, and see if the difference has changed. For example, if the reading you get going toward the chuck is that the reading in front is 10 and 5 at the back the difference is 5. If going away from the chuck the reading in front is 17 and 15 at the back, the difference is 2. This would indicate that the carriage is rotating when the feed direction is reversed. You may find that reversing the carriage before clamping it and facing will reduce your problem. Of course this will not change any wear in the cross slide.

Whoa! Lots of people will zoom in on the cross slide, but until you do a thorough test of the machine you can't be sure. You haven't said what type of machine it is, and that would help. The lathe may have multiple errors for example, and sometimes they can mask the real issue. I wouldn't be scraping anything until going back and ensuring the machine is set up properly, there's no twist in the bed, the headstock is square, etc etc.

First thanks for all the responses and comments.
The lathe is a jet 9x20. I use for smaller stuff and light work. My primary is a 14x40 optimum. Anyways
As for checking lathe I have done the tail stock aluminum bar test. Bar was 10" long, I cut 1" of each end. Got a difference of .002. Figured it wasn't to bad for 10" length and that's the tailstock.
When I faced a 1.5 piece of 6010 I checked with a square and the part tapers to the center. My tool is on center not leaving a numb. I mounted a interapid style gauge in the chuck ran the tip along the ground face of the compound slide base. With the compound slide closest to the operator the gauge was set to zero. I ran the slide away from the operator the gauge didn't move till about 2/3 the travel then gradual till the end of its travel. Total travel is about 4". This corresponded with the error I was getting in part.
Do I need a test bar that goes in the mt in spindle to check spindle alignment?

Jet 9X20???
Popcorn

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

Cadillac said:

First thanks for all the responses and comments.
The lathe is a jet 9x20. I use for smaller stuff and light work. My primary is a 14x40 optimum. Anyways
As for checking lathe Bar was 10" long, I cut 1" of each end. Got a difference of .002. Figured it wasn't to bad for 10" length and that's the tailstock.
When I faced a 1.5 piece of 6010 I checked with a square and the part tapers to the center. My tool is on center not leaving a numb. I mounted a interapid style gauge in the chuck ran the tip along the ground face of the compound slide base. With the compound slide closest to the operator the gauge was set to zero. I ran the slide away from the operator the gauge didn't move till about 2/3 the travel then gradual till the end of its travel. Total travel is about 4". This corresponded with the error I was getting in part.
Do I need a test bar that goes in the mt in spindle to check spindle alignment?

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I've read your post a few times but frankly can't make heads or tails of it. I don't know what you mean by "I have done the tail stock aluminum bar test." If you mean you have put a bar between centres and turned it at both ends, all you have done is checked your tailstock setover. It says nothing about whether your lathe is level, or will turn a taper. You need to firstly level your lathe, and then chuck a piece of stock unsupported in a chuck and carefully turn at least both ends (you can turn the whole lot if you want, but it's typically faster to relieve the middle of the bar and just turn two collars at the end). You will need a very sharp tool and light cuts so there's minimal deflection.

If the lathe is turning a taper, the chances are it's not properly levelled and the bed has a twist in it. You will need to get everything in the state it was in when it was at the factory (ie level) before being able to diagnose what may be the problem (if anything).

No you don't need a test bar. You can buy one of you'd like to stick one up your President and help the Chinese economy, but it's not normally needed unless you finish up having to seriously start screwing with things. Most of the time there's nothing much wrong with the lathe until some bozo starts screwing around with the headstock alignment etc. With all but the biggest POS, it's pretty safe to assume they shipped aligned, so if they're not aligned now there must be a good reason for it.

When you face the 1.5 in piece of aluminum cutting from the front way to the spindle axis, the cut you get SHOULD be slightly tapered in. In other words, if you have cut the outer edge round, and then face the bar, a straight edge should touch on the outer edge only, not in the middle. It should face "hollow or concave only" This is because the cross slide should not be exactly 90* to the spindle axis. The standard for this hollow is 0 to .02 mm per 300mm, or .0008 inches per 12 inches in diameter.

1.5 is 1/8 of 12, so the maximum of the hollow on your 1.5 in diameter piece should be .0001 inches. If you have a .0001 indicator, mount it to the cross slide and run from the outer edge to the center (the same path the facing tool took) the reading should not change---until after you cross the spindle axis. Between the spindle axis and be back of the piece, the indicator reading should increase to a maximum of .0002 inches.

It may be easier to understand this if you visualize using the compound set to cut a 60* center, then use your indicator on the compound to follow the tools path. It will not change its reading until it hits the other side, and then it is stuck in the hole as the angle is 120*. Cut a 45* taper, and then follow with the indicator, and the indicator hits the other side at 90*. Cut 5* taper, and the indicator hits a 10* taper on the other side of the spindle axis.

You cannot test the angle of the cross slide by measuring against its outer edge. (Unless you know it is parallel to the guiding dovetail (the one without the gib), and are rotating the indicator about spindle axis, and have already testing that spindle axis...)

The tailstock has nothing to do with the alignment of the headstock or the carriage

It would be very helpful if you could post some pictures or drawings of how you are doing your tests. Your descriptions are had to follow.

It sounds as if it is an import and those imports are not made to be precision, they are made to turn and to sell cheap. I doubt the machine will ever turn like a Monarch EE and for what he has a benchtop import that he can't show us a picture or name it he is lucky to get what he gets. The scraping and alignment of those imports is worse then bad when new. As the old saying goes, "Can't make a silk purse out of a sows ear!"

Thank u Pete and jr. Thats what I would like to hear what I should be getting and tips. NOT "jet garbage"or that I'm not listing what brand. I listed my brand in the second post. I will check alignment with a unsupported piece. I had stated that the only test performed I did was tailstock alignment and WASNT relevant to my problem.
Seems some people just want to belittle people or criticize their machines.
Where I live theirs a lot of American iron that i love and wanted to buy. But for me to pay2k on a machine that probably has been neglected crashed put away dry. Then to find out it needs to be rebuilt and parts are extinct or rediculously expensive. That's ok I'll stick with what I got.
But thanks for all the responses much appreciated.

Ahh I missed the small "jet" I saw 9 x 20....that's why I said Asian import. Many of those machines I believe were made in the same factory in China. This is why Practical Machinist management says no hobby Asian machine questions, as we wasted out time trying to tell you the info when that machine will never be accurate. I have had those machines apart and they are not designed to be accurate. I am not trying to be nasty or insult you, but rules are rules.

Richard King said:

I am not trying to be nasty or insult you, but rules are rules.

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And poor construction and design, are poor construction and design. So it goes

Rules are rules. Try finding a American made machine these days that's geared towards the hobbiest not production. As you all know maybe the two American brands are still made in Asia or 3/4 of the parts that go on the machine. Give me options for American made and I will buy American.
I feel that once I get this problem licked the lathe will be plenty accurate for my needs.

P.S. all the parts I make don't care where the machine came from just that their correct. Thanks again

I believe those rules exist due to non-catering to hobbyists.

Personally I wouldn't buy american "these days" I'd be buying Taiwanese (when referring to new manual lathes). which is what most folks do who need a manual lathe for production. the irony of all this is that this forum is obsessed with American iron because most of the guys here are in fact hobbyists at this late stage in the game (the majority of these beautiful old machines aren't being used in production anymore, at best some of them are in busy toolrooms like mine.)

A few folks still do use very fine American manual machines in production, and sometimes I envy them!

From my readings I would say 30% or more of the people asking questions on this site are hobbiest. I Joined to get professional advice from experienced people in the trade. If I wanted advice from someone that might know or just giving a opinion I would go to the home machinist sites.
I love American and would have a garage of American equip. But in my two years of searching I saw a lot of beat up shit. Either full rebuilds,or to big for my needs.
My hobby makes me good side money and teaches me day in and day out. That's a win win in my book. Thanks for your comments and criticism noted

Fwiw, I think the rules regarding Asian machines are relaxed in this forum. Not on the PM website mind you but on this, and perhaps a couple of other forums on pm. Please correct me if I am mistaken.
Were all jet machines made in Asia/china/chaiwan ?

Galaxy S4, Slimkat
If I wasn't married I'd quit fishing

Cadillac said:

hobbiest.

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Cadillac said:

hobbyist.

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Cadillac said:

hobbyist.

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fixed that for ya.

couldn't take it anymore... I know it's an American site but let's try to salvage the English language yea?

I was wondering this earlier. How does one survey the alignment of the cross slide ways?

apoc_101 said:

A few folks still do use very fine American manual machines in production, and sometimes I envy them!

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I've posted this before but I feel it's worth repeating.

Here in OKC we have a couple of manufacturers of valves, from 1/4" instrument valves on up to 10" ANSI 900# and beyond. Well I visited one of them a few years ago for a plant tour and it was supremely interesting. The tool crib was open, you needed something just grab it and tell the crib manager so he was aware of stock level.

Coolest part- they probably have the largest collection of W&S turret lathes in existence. Maybe 80-100 of them? And an old german guy named Heinz in there retrofitting them with DRO's and CNC controls. Of course they have big Okumas and other stuff, but a LOT of their small round work is turned and tapped on old American iron. I should have taken some pics.